A sleazy FDNY smoke eater was busted yesterday for calling in false alarms, and then stealing cash from colleagues when they left their firehouses to respond to the phony calls, authorities said.

Joseph Keene, 34, of Hicksville, LI, used his own cellphone to call in three “emergencies” in Staten Island and Queens in May and June, according to a shocking Department of Investigation report.

“This guy committed the two cardinal sins of a firefighter,” said an outraged colleague at one of the Staten Island firehouses.

“He called in fake jobs, the exact opposite of what we do, and does this to steal from the brothers. Unbelievable, it’s just unconscionable.”

In the first incident, on May 29, Keene allegedly called in a report of a gas odor near Forrest and Veltman avenues in Staten Island, which resulted in Ladder Co. 83 on Jewett Avenue responding.

While the firefighters were investigating, Keene snuck into the firehouse and swiped $150 to $200, authorities said.

On June 2, he reported a transformer sparking at Victory Boulevard and Forrest Avenue on Staten Island.

When Ladder 80 responded, he went to their empty firehouse on Castleton Avenue and allegedly stole about $500.

Nine days later, the disgraced firefighter made a third phony 911 call reporting a gas odor at Jamaica Avenue and Little Neck Parkway in Queens.

Engine 251 went to investigate, and Keene then allegedly entered their firehouse on Union Turnpike and made his single largest haul, about $1,200 in cash.

Finally, on July 17, Keene reported for work at an FDNY facility on Randalls Island and took $40 to $60 from the employee locker area, DOI said. Later that same day, he entered Engine 263/Ladder 117 on Astoria Boulevard in Queens while the firefighters were out covering for a unit battling a blaze in The Bronx, and allegedly took $100.

Investigators traced the phone calls back to a cellphone number registered to Keene. He also was captured on surveillance video entering the Engine 251 firehouse, and a witness spotted him at the firehouse on Astoria Boulevard shortly before the thefts there were discovered.

DOI and NYPD investigators finally confronted Keene Thursday, and he admitted to both the phone calls and the thefts, authorities said.

Keene, who earned $76,488 in 2012, was arraigned in Queens Criminal Court yesterday on felony charges of falsely reporting an incident, grand larceny and burglary, as well as a petty larceny charge. He was released on $5,000 bond.